UC San Diego

Blood transfusions are used to treat reduced O2-carrying capacity consequent to anemia. In many cases anemia is caused by a major blood loss, which also creates a state of hypovolemia. Whereas O2 transport capacity is restored by increasing levels of circulating Hb, transfusion does not resolve the hypoperfusion, the hypoxia and the inflammatory cascades initiated during the anemia and hypovolemia. This explains why blood transfusion is not always an effective treatment and why transfusion of stored blood has been associated with increased morbidity and mortality, especially in patient populations receiving multiple transfusions. Epidemiologic data indicate that adverse events after transfusion are relatively common, having a great impact on the patients outcome and on the costs of public health. In this chapter, we explain why classical transfusion strategies target the reversal of hypoxia only, but do not address the inflammatory cascades initiated during anemic states and the importance of the flow and vascular endothelium interactions. We also establish the relation between red blood cells storage lesions, limited NO bioavailability and transfusion-associated adverse events. Lastly, we explain the potential use of long-lived sources of bioactive NO to reverse the hypoxic inflammatory cascades, promote a sustained increase in tissue perfusion and thereby allow transfusions to achieve their intended goal. The underlying premise is that adverse effects associated with transfusions are intimately linked to vascular dysfunction. Understanding of these mechanisms would lead to novel transfusion medicine strategies to preserve red cell function and to correct for functional changes induced by hemoglobinopathies that affect cell structure and function.